Conventionally most water meters include a totalizing counter which is driven mechanically, i.e. rotation of the spinner drives the index wheels of the meter via a transmission which is mechanical and/or magnetic.
More recently, proposals have been made to detect rotation of the spinner by means of a proximity sensor placed facing a rotary element integral with the spinner and designed to detect the passage of a mark placed eccentrically on the rotary element. For example, the proximity detector may be based on an inductive method, in which case the mark is constituted by a material whose magnetic and/or electrical characteristics are different from the remainder of the rotary element. Such detectors nevertheless suffer from drawbacks.
Firstly there are various parameters that vary as a function of time; for example for a water meter integrated in a calorimeter, these parameters include: the temperature of the water that may cause the characteristics of the detector to vary; the power supply voltage to the detector circuit, in particular when the power supply is provided by a battery; and the distance between the proximity detector and the rotary element because of the way the spinner rises at high speed.
In general, there are various parameters that vary from one detector to another and that are difficult and expensive to bring under control in mass production. For example, for an inductive type of detector, such parameters include the inductance of the coil and its Q-factor, which means that each detector needs to be calibrated or else that components need to be sorted.
An object of the invention is to remedy these drawbacks by using a system that is adaptive and includes at least two proximity detectors.